ExecJS::ProgramError: Unexpected token punc «(», expected punc «:» when running rake assets:precompile on production

Question

When deploying my Rails app I get the following error:

rake aborted!
   ExecJS::ProgramError: Unexpected token punc «(», expected punc «:» (line: 15, col: 14, pos: 265)

   Error
   at new JS_Parse_Error (/tmp/execjs20150524-4411-1p45n63js:2359:10623)
   at js_error (/tmp/execjs20150524-4411-1p45n63js:2359:10842)
   at croak (/tmp/execjs20150524-4411-1p45n63js:2359:19086)
   at token_error (/tmp/execjs20150524-4411-1p45n63js:2359:19223)
   at expect_token (/tmp/execjs20150524-4411-1p45n63js:2359:19446)
   at expect (/tmp/execjs20150524-4411-1p45n63js:2359:19584)
   at /tmp/execjs20150524-4411-1p45n63js:2359:28513
   at /tmp/execjs20150524-4411-1p45n63js:2359:19957
   at expr_atom (/tmp/execjs20150524-4411-1p45n63js:2359:27269)
   at maybe_unary (/tmp/execjs20150524-4411-1p45n63js:2359:30019)new JS_Parse_Error ((execjs):2359:10623)
   js_error ((execjs):2359:10842)
   croak ((execjs):2359:19086)
   token_error ((execjs):2359:19223)
   expect_token ((execjs):2359:19446)
   expect ((execjs):2359:19584)
   (execjs):2359:28513
   (execjs):2359:19957
   expr_atom ((execjs):2359:27269)
   maybe_unary ((execjs):2359:30019)

The file in question is valid, it works on localhost. I also tried running rake assests:precompile on localhost, it all passes. Finally, I tried to remove the content from the file, git push and redeploy - still got the same error. Only completely removing the file and re-deploying helps.

Would appreciate any ideas.

Answer 1

Here I found help for the same problem you had.

Run rails console and:

JS_PATH = "app/assets/javascripts/**/*.js"; 
Dir[JS_PATH].each do |file_name|
  puts "\n#{file_name}"
  puts Uglifier.compile(File.read(file_name))
end

It will show you the file and the line where the Uglifier is making the problem.

Answer 2

I suspect, in that js file, you have something like the following:

var User = {
    getName() {
        alert("my name");
    }
}

Replacing it with the right format,

var User = {
    getName: function() {
        alert("my name");
    }
}

worked for me.

Error is clearly saying, it's expecting ":" but it found "(".

Answer 3

Just encounter the same issue.

My case is someone used syntax that's only support since ES2015, ex

function someThing(param = true) {
    // do something here
};

while this is not supported in our environment.

And the error messages is actually generated by Uglifer.

Answer 4

I'm not sure of your build chain, but I got here by pasting the same error message into Google.

That is called 'shorthand properties' in ES2015. I'm using Babel 6 with Gulp and needed to do an npm install babel-plugin-transform-es2015-shorthand-properties --save-dev and add that transform to my babel plugins.

.pipe(babel({
    plugins: [
        'transform-es2015-shorthand-properties'
    ]
}))

https://github.com/babel/babel/tree/master/packages/babel-plugin-transform-es2015-shorthand-properties

Answer 5

I could use https://skalman.github.io/UglifyJS-online/ to identify the correct line number where the issue was. Thankfully, at least the correct file which had an issue was pointed out by grunt uglify

Answer 6

In my case problem with function definition like,

function someFunctionName(param1, param2=defaultValue){
  //code 
}

Due to above function definition I was getting error, as it is not supported by Uglifier. Default parameters is ES6/ES2015 language specification.

For solution to above problem you can refer Set a default parameter value for a JavaScript function

Answer 7

If Radovan's answer isn't working for you due to a problem in a library instead of your code, you can try upgrading Uglifier and enabling ES6 compilation.

Gemfile.lock

gem 'uglifier', '~> 4.1'

config/environments/production.rb

config.assets.js_compressor = Uglifier.new(harmony: true)

Answer 8

As the backtrace doesn't provide information about the corrupted file, for me the best way to identify the error is use git bisect.

It allows you to find the commit that introduces a bug.

Let's suppose you are on master, first you start git bisect:

$ git bisect start
$ git bisect bad 

Then you go back to a previous, working revision, let's suppose 20 revision ago.

$ git checkout HEAD~20

You run the same command

$ RAILS_ENV=production rake assets:precompile

If it works you mark revision as good:

$ git bisect good.

git will jump to another revision, you run same command again (assets:precompile) and bassed on the output mark it as good / bad.

In less than 1 minute you should be able to find what's the commit that introduced the issue.